Electrolysis has been employed in the removal of solid particles from liquid. In known techniques, gas bubbles developed by electrolysis rise in the liquid and capture the solid particles and bring them along up to the surface where they are skimmed off in some suitable way. The ability to purify water by such bubbling techniques, however, has been comparatively small due to the fact that the bubbles, in striving to rise upwards linearly strike against the walls of the working vessel and one another, so that the bubbles break and the solid particles are separated from the gas bubbles.
In order to eliminate these drawbacks the applicant has proposed forming an aluminum anode by using aluminum flock which is circulated in the material being purified, in order to absorb the impurities in the material, while rising to the surface for removal in ordinary manner.
The present invention is directed to the provision of a method and apparatus which has been found to considerably improve the latter method, while reducing power consumption per unit volume of purified liquid. According to the invention one or more aluminum electrodes are kept at a given distance from the negative pole, and the emulsion being treated, or the water, is run into or near the space between the electrodes to contact these electrodes. The flock resulting from this treatment is then separated in a known manner. The electrodes are kept just a few millimeters from one another, the aluminum anode preferably being above the cathode, so that it extends end to end with or forms an angle with the cathode. In accordance with the invention it is desired to obtain an electric flow path which is narrow or small in cross-section with correspondingly stronger flow. This is accomplished, for instance, by using one or more thread-like aluminum anodes which are situated at right angles or obliquely with respect to the cathode, the latter of which suitably is made of stainless steel into the form of a flute, plane, rotating roller or a plate, an endless band or the like. The anode may be fed in many different ways such as, for instance,by the power of its own weight, or by means of a mechanical device such as drawing wheels engaging it. The distance from the anode to the cathode may be regulated simply by fitting an insulating member between them, which the anode is directed to strike. The anode can also be fed according to a given program, or by using suitable feeler members for measuring the distance between the parts and a suitable mechanism in between for keeping to a program for feed advance of the anode.
The material being purified is run at least some distance in contact with the electrode before arriving to the space between the electrodes. This may be accomplished simply by flowing the material to be purified from its storage tank in an electrode guiding member which may be, for instance, a pipe, an inclined surface, a flute, or the like. The material to be purified may also be directed from one or more nozzles into the space between the electrodes.
The electrodes are preferably coupled to a low-tension direct-current source of 12 volts, for instance. A suitable current strength is for example 1.5-2 ampere. By using suitable electrodes and an electrode distance of a few millimeters a power consumption of nearly half a watt per liter material to be purified has been attained in tests. This is only a fraction of the energy previously needed for corresponding purification. In the process according to the invention a very strong foaming action is observed at the electrodes, with plenty of flock and hydrogen development. If the electrode gap is located in the air space, one can actually see the flocks and the droplets of clear pure water dropping from the reaction place.